BACKGROUND:
The optimal timing of coronary intervention in patients with non-ST-segment elevation acute coronary syndromes (NSTE-ACSs) is a matter of debate. Conflicting results among published studies partly relate to different risk profiles of the studied populations.

PURPOSE:
To do the most comprehensive meta-analysis of current evidence on early versus delayed invasive treatment in NSTE-ACS.

DATA EXTRACTION:
Data were extracted for populations, interventions, outcomes, and risk of bias. All-cause mortality was the prespecified primary end point. The longest follow-up available in each study was chosen. The odds ratio with 95% CI was the effect measure.

DATA SYNTHESIS:
Seven RCTs (5370 patients) and 4 observational studies (77 499 patients) were included. Early intervention was less than 20 hours after hospitalization or randomization for RCTs and 24 hours or less for observational studies. Meta-analysis of the RCTs was inconclusive for a survival benefit associated with the early invasive strategy (odds ratio, 0.83 [95% CI, 0.64 to 1.09]; P = 0.180); a similar result emerged from the observational studies. With early versus late intervention, the odds ratios in the RCTs were 1.15 (CI, 0.65 to 2.01; P = 0.63) and 0.76 (CI, 0.56 to 1.04; P = 0.090) for myocardial infarction and major bleeding during follow-up, respectively.

LIMITATION:
Current evidence from RCTs is limited by the small overall sample size, low numbers of events in some trials, and heterogeneity in the timing of intervention and in patient risk profiles.

CONCLUSION:
At present, there is insufficient evidence either in favor of or against an early invasive approach in the NSTE-ACS population. A more definitive RCT is warranted to guide clinical practice.